IJSART - Volume 2 Issue 7 –JULY 2016 ISSN [ONLINE]: 2395-1052 Design and Simulation of Manual Rack and Pinion Steering System

Prashant L Agrawal1, Sahil Shaileshbhai Patel2, Shivanshu Rajeshbhai Parmar3 1 Department of Automobile Engineering 2 Department of Mechanical Engineering 1, 2 L.J institute of engineering and technology

Abstract- Manual rack and pinion steering systems are commonly used due to their simplicity in construction and compactness. The main purpose of this paper is to design and manufacturemanual rack and pinion steering system according to the requirement of the vehicle for better manoeuvrability. Quantities like turning circle radius, steering ratio, steering effort, etc. are inter-dependent on each other and therefore there are different design consideration according to the type of vehicle. The comparison of resultis shown using tables which will help to design an effective steering for the vehicle. A virtual rack and pinion assembly Fig. 1. Ackermann Principle and Inner wheel and Outer wheel can be created using software like SOLIDWORKS and ANSYS. angles

Keywords- Steering ratio, steering wheel torque, inner wheel and The intention of Ackermann geometry is to prevent outer wheel angle, Rack and Pinion steering. the tyres from slipping outwards when the wheels follows around a curve while taking a turn. The solution for this is that I. INTRODUCTION all wheels to have their axles settled as radii of circles with a common centre point. Since the rear wheels are fixed, this In this paper a virtual prototype of rack and pinion centre point must lie on a line extended from the rear axle. So assembly with complete SOLIDWORKS geometry is we need to intersect the front axle to this line at the common proposed to enhance and facilitate steering response by centre point. While steering, the inner wheel angle is greater varying the different parameters employed during its design than outer wheel angle. So for obtaining different results we and manufacturing. It is important to know how the different need to vary the parameters in order to obtain desired steering aspects like steering ratio, pinion diameter, rack length etc. geometry. govern the working of the mechanism. The possibility of decreasing lock to lock steering degree has motivated us to II. CALCULATIONS work upon this system. In the figure below it is shown that the total length of According to Ackermann Steering geometry, the the vehicle from the center of the front wheel to center of the outer wheels moves faster than the inner wheels, therefore, the rear wheel is called Wheel Base (b). Similarly, the total length equation for correct steering is: between center of the front left wheel to center of front right b Cot Φ – Cot θ = /l wheel is called Wheel Track (t). The distance between the two pivot joints of steering system is called Kingpin Centre to In the image shown below, Centre distance (k). The calculation of Ackermann angle is Φ = outer wheel angle shown below: θ = inner wheel angle b = track width

L = wheelbase α = Ackermann angle

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IJSART - Volume 2 Issue 7 –JULY 2016 ISSN [ONLINE]: 2395-1052

TABLE I. PREDEFINED VALUES OF THE VEHICLE Where, Y= arm base R= arm radius assumed to be 5” Sin 20.80 = Y/R Y=1.7” Thus the value of Ackermann arm base is 1.7”

B. TURNING CIRCLE RADIUS:

Turning circle radius is the full diameter of the smallest circle traced by the wheels when taking a full turn,

() T = + OF

() T = − IF

Outer wheel turning circle radius:

Fig. 2. Wheel Track, Wheel Base and Kingpin C-C Distance TIF = 1.96 m Inner wheel turning circle radius: -1 Ackermann angle (α) = tan [(kingpin distance/2) / TOF = 2.695 m wheelbase] -1 = tan [(38/2) / 50] Average turning circle radius (TAVG) = 2.35 m -1 = tan [0.38] = 20.80 C. RACK AND PINION CALCULATIONS:

But, according to Ackermann geometry for correct TABLE II. Values of the quantities used in calculations steering, the below equation should be satisfied, thus by calculating Inner Wheel angle and Outer Wheel angle practically were:

Φ = 27˚ θ = 43˚

We know that, module = Module of rack and pinion = 1.5 mm

Fig. 3. Ackermann Arm Radius Steering wheel lock to lock angle is the total rotating capacity of the steering wheel (i.e. -270˚ to +270˚). Steering A. ARM BASE CALCULATIONS: Ratio is the ratio of Input from the steering wheel (in degrees) to the output on the wheels (in degrees). Arm base is a part of steering knuckle, to which the tie rods are attached. We know that sine angle in a triangle is Steering wheel lock to lock turns / angle = 1.5 turns/ 540˚ the ratio of opposite side to hypotenuse, thus, Steering ratio = 270 / 43 = 6.2: 1 = 6:1 (approx)

Sin α = Y/R

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IJSART - Volume 2 Issue 7 –JULY 2016 ISSN [ONLINE]: 2395-1052

D. STEERING WHEEL TORQUE CALCULATION: Similarly, for predefined Rack lengths, the values of Inner wheel angle, Outer wheel angle, Lock to Lock Steering The torque required to rotate the steering wheel by wheel angles and Average Turning circle radius are shown the driver is called Steering Wheel Torque (WT). below, the table shows that Rack length is directly proportional to the steering wheel lock to lock angle and The calculations for steering wheel toque as follows, inversely proportional to average turning circle radius.

B T = Wu + E TABLE IV. Different quantity values for various rack lengths 8

T = kingpin torque W = axle weight = 50 kg = 120 lbs (the axle weight for every vehicle is different and it is not the total weight of the vehicle) = co-efficient of friction = 0.7 (assumed to be 0.7 for most of the road condition) E = kingpin offset = 55mm = 2.1” B = width of tire = 7”

The above values will be different for every vehicle.

7 T = 50 ∗ 0.7 + 2.1 8 =113.60 inch-lbs Where, =12.84 N-m Φ = outer wheel angle θ = inner wheel angle ∗ Torque on Pinion gear = TAVG = Average turning circle radius

.∗. III. CAD MODEL = .0165 = 513.6 N We have designed complete assembly of rack and pinion in SOLIDWORKS 2015, the complete design of rack Steering wheel torque = 513.6 * 6 * 0.0254 and pinion and its assembly in SOLIDWORKS 2015 is shown = 78.27 N-m below:

The values of Steering Effort, Gear ratio, Steering Ratio for different predefined Pinion sized are shown below, the table shows that the change in pinion size is directly proportional to the steering effort applied by the driver and the steering ratio. And similarly pinion size is inversely proportional to Total steering lock to lock angle. The turning circle radius is independent of pinion size and remains constant in the table. Therefore, for vehicles with heavy axle loads should prefer smaller pinion pitch circle diameter.

TABLE III. Different quantity values for various Pinion Sizes IV. ANALYSIS OF COMPONENTS

Analysis is process of analysing the components by applying load, temperature, pressure etc. and obtaining the values such as stresses (bending, tangential and normal), deformations, safety factor etc. in order to determine the safety of the components when done in practical. These Analyses gives optimum result of safety of components and minimize the chances of failure. Page | 3 www.ijsart.com

IJSART - Volume 2 Issue 7 –JULY 2016 ISSN [ONLINE]: 2395-1052

Three major analyses of rack and pinion on Ansys 15.0 are commonly used in light weight vehicles. The values calculated carried out here: in the paper may differ practically due to steering linkages error or due to improper steering geometry, so these values are 1) Total Deformation useful to understand the interdependency of the quantities on 2) Equivalent Stress each other and to design a ideal manual rack and pinion 3) Factor of Safety system for the vehicle. a) Total Deformation REFERENCES

[1] R.S. Khurmi, J.K. Gupta “Theory of Machines”, S. Chand & Company Pvt. Ltd., Vol 1, 14th Edition, 2014.

[2] S.K. Gupta “A Textbook of Automobile Engineering”, S. Chand & Company Pvt. Ltd., Vol 1, 1st Edition, 2014.

[3] Saket Bhishikar, Vatsal Gudhka, Neel Dalal, Paarth Mehta, Sunil Bhil, A.C. Mehta “Design and Simulation of 4 Wheel Steering System”, International Journal of b) Factor of Safety Engineering and Innovative Technology (IJEIT), Volume 3, Issue 12, June 2014.

c) Equivalent Stress

Material Type: EN24 Ultimate Tensile Strength = 850 MPa Maximum Stress Obtained = 18.845 MPa Factor of Safety = 15 Maximum Deformation = 15.5757 x 10-4mm Thus after the analyses of components The Design is Completely Safe.

V. CONCLUSION

The manual rack and pinion steering system is not used in heavy weight vehicles due to high axle loads, although it is simple in design and easy to manufacture, therefore it is Page | 4 www.ijsart.com